U.S. patent number 4,880,419 [Application Number 07/284,049] was granted by the patent office on 1989-11-14 for absorbent article with internal wicking means.
This patent grant is currently assigned to Chicopee. Invention is credited to Irving S. Ness.
United States Patent |
4,880,419 |
Ness |
November 14, 1989 |
Absorbent article with internal wicking means
Abstract
An absorbent article comprising at least two discrete
superabsorbent containing layers and a wicking means extending
about and between the superabsorbent containing layers.
Inventors: |
Ness; Irving S. (Palmetto
Dunes, SC) |
Assignee: |
Chicopee (New Brunswick,
NJ)
|
Family
ID: |
27387214 |
Appl.
No.: |
07/284,049 |
Filed: |
December 14, 1988 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
152208 |
Feb 3, 1988 |
4842594 |
|
|
|
889448 |
Jul 23, 1986 |
|
|
|
|
721832 |
Apr 10, 1985 |
|
|
|
|
525850 |
Aug 24, 1983 |
|
|
|
|
Current U.S.
Class: |
604/368;
604/378 |
Current CPC
Class: |
A61F
13/53427 (20130101); A61F 13/53708 (20130101); B32B
5/22 (20130101); A61F 13/534 (20130101); A61F
13/53409 (20130101); A61F 2013/15487 (20130101); A61F
2013/530335 (20130101); A61F 2013/530343 (20130101); A61F
2013/53035 (20130101); A61F 2013/530481 (20130101); A61F
2013/530802 (20130101); A61F 2013/53445 (20130101); A61F
2013/53721 (20130101); A61F 2013/53786 (20130101) |
Current International
Class: |
A61F
13/15 (20060101); B32B 5/22 (20060101); A61F
013/16 () |
Field of
Search: |
;604/367,368,369,378,379,358,385.1,374,375 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1492430 |
|
Mar 1970 |
|
DE |
|
6707397 |
|
Dec 1967 |
|
NL |
|
7701851 |
|
Aug 1978 |
|
NL |
|
Primary Examiner: Yasko; John D.
Attorney, Agent or Firm: Schuler; Lawrence D.
Parent Case Text
This is a continuation of application Ser. No. 152,208, filed Feb.
3, 1988 now U.S. Pat. No. 4,842,594, which is a continuation of
application Ser. No. 889,448, filed July 23, 1986 now abandoned,
which is a continuation of application Ser. No. 721,832, filed Apr.
10, 1985, which is a continuation-in-part of application Ser. No.
525,850, filed Aug. 24, 1983 now abandoned.
Claims
I claim:
1. An absorbent article comprising at least two discrete
superabsorbent containing layers and a continuous wicking means
extending about and between the superabsorbent containing
layers.
2. An absorbent article as in claim 1 wherein said wicking means
comprises a wicking layer and a fluid transfer means between the
wicking layer and each discrete superabsorbent containing layer,
said fluid transfer means being adapted to drain liquid from the
wicking layer and make it available to the superabsorbent material
in the superabsorbent containing layer.
3. An absorbent article as in claim 2 wherein said wicking means
comprises a fluid transfer means having a higher capillary pressure
than the wicking layer.
4. An absorbent article as in claim 1 wherein said superabsorbent
containing layers comprise a superabsorbent material dispersed
within a fibrous layer.
5. An absorbent article as in claim 1 wherein said superabsorbent
containing layers comprise a superabsorbent material dispersed
within a cellular foam material.
6. An absorbent article as in claim 1 wherein said superabsorbent
containing layers comprise a film comprising superabsorbent
material.
7. An absorbent article as in claim 1 wherein said wicking layer
comprises an acrylic fiber fabric, wood pulp fibers, peat moss, or
tissue material.
8. An absorbent article as in claim 1 wherein said fluid transfer
means comprises tissue material.
9. An absorbent article as in claim 1 further comprising a partial
outer wrap of fluid impermeable material.
10. A disposable diaper comprising a backing sheet, at least two
adhesive tape tabs affixed to said backing sheet, and the absorbent
article of claim 1 affixed to said backing sheet.
11. An absorbent article as in claim 1 wherein said superabsorbent
containing layers comprise a superabsorbent material dispersed upon
a fibrous layer.
12. An absorbent article according to claim 2 wherein said fluid
transfer means comprises a layer coextensive with said wicking
layer.
13. An absorbent article according to claim 2 wherein said wicking
means comprises a wicking layer incorporated between two layers of
fluid transfer means.
Description
BACKGROUND OF THE INVENTION
The use of superabsorbents in absorbent articles permits a
substantial reduction in the bulk of the absorbent article.
However, attempts to utilize superabsorbent materials in absorbent
structures such as diapers and sanitary napkins have met with
limited success. It is often difficult to "fix in place" or secure
superabsorbents within the absorbent article. U.S. Pat. No.
3,971,379 discloses absorbent articles wherein a layer of
superabsorbent is folded or rolled with another absorbent component
of the absorbent article. Secondly, superabsorbent materials absorb
and retain hundreds of times their weight of fluids, but they do
not easily wick fluids. In an absorbent article, rapid swelling of
the superabsorbent together with its lack of wicking ability can
create a fluid "block", preventing the utilization of the remainder
of the superabsorbent, or other absorbent materials in the
absorbent article.
New methods of utilizing superabsorbents into absorbent articles
focus on methods of incorporating the superabsorbent into a fibrous
structure so as to avoid the blocking problem. U.S. Pat. No.
4,105,033 discloses a method of incorporating a superabsorbent into
a fibrous structure, and U.S. Pat. No. 4,226,237 discloses a more
elaborate fibrous structure of absorbent fibers and peat moss, into
which superabsorbent may be distributed.
The present invention involves a new approach to the use of
superabsorbents in an absorbent article. Rather than attempt to
create new fibrous structures wherein the superabsorbent is so
dispersed as to prevent blocking, the present invention may use
known fibrous materials containing superabsorbents which materials
when used alone may block. In the absorbent article of the present
invention, the superabsorbent may be dispersed within a fibrous
structure or cellular foam or may be present in a film, alone or
together with other ingredients. According to the present
invention, an internal wicking means is provided within the
absorbent article to bring the fluid to the superabsorbent. The
wicking means is wrapped or folded about discrete layers containing
the superabsorbent.
Methods of folding absorbent fibrous materials to form absorbent
articles are shown in U.S. Pat. No. 2,952,259. However, there is no
teaching of superabsorbents or internal wicking means.
SUMMARY OF THE INVENTION
The present invention comprises an absorbent article having
discrete superabsorbent containing layers. The absorbent article
has a wicking means which is wound about and between the
superabsorbent containing layers. The wicking means comprises a
wicking layer, and a fluid transfer means between the wicking layer
and the superabsorbent containing layers. The superabsorbent
containing layers may comprise superabsorbent ingredients dispersed
within a fibrous layer or upon a fibrous layer, or superabsorbent
dispersed within a cellular foam material, or films made partially
or entirely of superabsorbent materials. Acrylic fibers, peat moss,
wood pulp fibers, or tissue or mixtures thereof may provide the
wicking layer. The fluid transfer layer is formed of similar
materials, but provides a higher capillary pressure for the liquid
than that possessed by the wicking layer. A partial outer wrap of
fluid impermeable material may be disposed about all but one major
surface of the absorbent article. In a disposable diaper the
plastic film partial outer wrap may be sealed to the outer surface
of the disposable diaper, reinforcing the diaper and enhancing the
repositionability of adhesive tape tabs thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic cross-section of one embodiment of the
absorbent article of the present invention;
FIG. 2 shows a cross-section of one embodiment of the absorbent
article shown schematically in FIG. 1;
FIG. 2A shows a cross-section of another embodiment of the
absorbent article shown schematically in FIG. 1;
FIG. 3 shows a cross-section of another preferred embodiment of the
absorbent article of the present invention;
FIG. 4 shows a cross-section of a disposable diaper incorporating
the absorbent article of the present invention;
FIG. 5 shows a cross-section of a preferred embodiment of a
disposable diaper incorporating the absorbent article of the
present invention; and
FIG. 6 shows a perspective view of the diaper of FIG. 5.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises an absorbent article which utilizes
superabsorbent materials in a novel way. According to the present
invention, an internal wicking means is utilized to move fluid
within an absorbent article that contains superabsorbent
materials.
As shown schematically in FIG. 1, one embodiment of the absorbent
article of the present invention shown generally at 10 comprises at
least two discrete layers 12 having a superabsorbent material
incorporated therein. The absorbent article further comprises a
wicking means 14 which extends in an S-shape wound about and
between the superabsorbent layers. The present invention does not
rely on the form or construction of the superabsorbent containing
layer, and many varieties of materials incorporating superabsorbent
agents may be utilized. For instance, the superabsorbent containing
layer may comprise superabsorbent material incorporated within a
fibrous layer, or a cellular foam layer. The method of
incorporating the superabsorbent into the fibrous layer or cellular
foam is not critical as it is not required that fluid pass through
the superabsorbent containing layer, but only that the surfaces of
the superabsorbent material is contacted by the liquid. Indeed,
according to the present invention, the superabsorbent containing
layers may comprise films made wholly or in part of superabsorbent
materials. In the absorbent article of the present invention, the
superabsorbent containing layers need not wick or transport fluid
as the internal wick of the absorbent article brings the fluid to
the superabsorbent material. Hence, when the superabsorbent
material within the layers swells, it tends not to block the
movement of the fluid through the absorbent article. If the
superabsorbent in any particular part of the absorbent article
swells or reaches saturation, the internal wicking means merely
moves the fluid to be absorbed on to the next available
superabsorbent material.
The following test data demonstrate the superiority of Applicant's
absorbent article having internal wicking means. The absorbent
capacity of three diaper structures incorporating the absorbent
article of the present invention as described in FIG. 1 was tested.
In the test procedure used, which is intended to simulate diaper
use, the diapers are fastened around a lifesize doll and test
solution is poured through the doll into the diaper in 50
milliliter aliquots, with a twenty minute wait between aliquots.
The test is stopped at the first indication of a leak. The diapers
are weighed before and after the test so that the amount of liquid
absorbed by the diaper can be determined. Each of the diapers had a
co-extruded Visqueen polypropylene film backing (171/2".times.12")
and a similarly sized facing material of 100 percent embossed
polypropylene 0.7 oz/yd..sup.2 fabric. The superabsorbent
containing layers comprise 8 gm/ft.sup.2 Henkel fabric S6P
manufactured by the Henkel Corporation. The Henkel fabric comprises
S6P-147, a ceric ion catalyzed starch acrylonitrile graft polymer
in powder form, sandwiched between two layers of tissue. In diaper
No. 1, the absorbent body of the diaper, contained between the
facing and backing sheet, comprised two layers of the Henkel
superabsorbent fibrous layer S6P and had no internal wick. The
absorbent capacity was 72.8 grams. In diaper No. 2, the absorbent
article, incorporated between the backing and the facing comprises
two layers of the same Henkel fabric with an S-shaped wicking layer
of tissue. The absorbent capacity of diaper No. 2 was 165.9 grams.
In diaper No. 3, the absorbent article, contained between the
backing sheet and the facing, comprised two layers of the same
Henkel superabsorbent fibrous layer, and an S-shaped internal
wicking layer of acrylic fiber fabric. The absorbent capacity of
diaper No. 3 was 179.1 grams.
FIG. 2 discloses one embodiment of the absorbent article of the
present invention shown schematically in FIG. 1. In this
embodiment, the absorbent article shown at 20 comprises
superabsorbent containing layers 22 and an internal wicking means
24 which comprises a wicking layer 26 and a fluid transfer means
28. The wicking layer 26 may comprise any material which has good
wicking properties. It is not required that this material have good
absorbent capacity or be able to retain fluids under stress.
Suitable materials for use as the wicking layer are acrylic fibers,
wood pulp fibers, tissue material, or peat moss. Fluid transfer
means may be present between the wicking layer and at least the
major surfaces of the superabsorbent containing layers. The fluid
transfer means is any of the materials suitable for the wicking
layer but the material is in a form so as to provide a higher
capillary pressure in the fluid transfer means than that provided
by the wicking layer. In the examples listed above, the tissue
layers of the Henkel fabric serve as the fluid transfer means. The
fluid transfer means 28 effects the transfer of the fluid from the
wicking layer to the superabsorbent containing layer. The use of
the intermediate fluid transfer means aids in keeping the internal
wicking means or pathway open at all times and allows the wicking
layer to wick while the fluid transfer means holds and gradually
releases the fluid for absorption in the superabsorbent containing
layers.
The higher capillary pressure fiber fluid transfer means provides
the mechanism for draining a substantial portion of the liquid from
the wicking layer and making it available to the superabsorbent
material. As the superabsorbent material takes liquid from the
fluid transfer means, the fluid transfer means takes liquid from
the wicking layer. What appears to be only a small difference in
capillary pressure, is all that is required for the fluid transfer
means to attract and drain the wicking layer of liquid the latter
has received. The force causing a liquid to enter a cylindrical
capillary is expressed by the equation: ##EQU1## wherein the force
is represented by the capillary pressure and: P is the capillary
pressure,
v is the surface tension of the liquid,
.theta. is the liquid-fiber contact angle, and
r is the capillary radius.
With a given liquid, the pressure (capillary force) increases with
the cosine of the liquid-fiber contact angle (reaching a maximum
where the angle is zero) and also increases with narrower capillary
radii so that narrower capillaries will draw liquid from the wider
ones.
The relative wickability between the fluid transfer means and the
wicking layer is affected by both the relative densities of the
layers and the relative wettability of the individual fibers in
each layer. The individual fibers of the fluid transfer means have
substantially smaller liquid-fiber contact angles than those of the
wicking layer overcoming the density difference and providing a
significant overall increase in capillary pressure to absorb liquid
into the fluid transfer means.
The fluid transfer means fibers and the density of the layer are
selected to create the small, but significant difference in
capillary pressure from the wicking layer.
The superabsorbent material used in the superabsorbent containing
layer is generally a water-insoluble but water-swellable polymeric
substance capable of absorbing water in an amount which is at least
10 times the weight of the substance in dry form. The
superabsorbent material is in the form of particles, or fibers, or
spheres, or bits of film, or globules or the like. In addition, the
superabsorbent may be formed in situ by spraying a liquid monomer
solution onto a fibrous web or fabric and subsequently polymerizing
and cross-linking the monomers to provide the water-insoluble,
water-swellable polymeric substance.
One type of suitable superabsorbent in the form of particles or
fibers may be described chemically as having a backbone of natural
or synthetic polymers with hydrophilic groups or polymers
containing hydrophilic groups being chemically bonded to the
backbone or an intimate admixture therewith. Included in this class
of materials are such modified natural and regenerated polymers as
polysaccharides including, for example, cellulose and starch and
regenerated cellulose which are modified by being carboxyalkylated,
phosphonoalkylated, sulphoalkylated or phosphorylated to render
them highly hydrophilic. Such modified polymers may also be
cross-linked to improve their water-insolubility.
These same polysaccharides may also serve, for example, as the
backbone onto which other polymer moieties may be bonded by graft
copolymerization techniques. Such grafted polysaccharides and their
method of manufacture are described in U.S. Pat. No. 4,105,033 to
Chatterjee et al. and may be described as polysaccharide chains
having grafted thereon a hydrophilic chain of the general formula:
##STR1## wherein A and B are selected from the group consisting of
--OR.sup.3, --O (alkali metal), --OHNH.sub.3, --NH.sub.2, wherein
R.sup.1, R.sup.2 and R.sup.3 are selected from the group consisting
of hydrogen and alkyl having 1 to 4 carbon atoms, wherein r is an
integer having a value of 0 to about 5000 or more, s is an integer
having a value of 0 to about 5000 or more, r plus s is at least
500, p is an integer having a value of zero or 1 and q is an
integer having a value of 1 to 4. The preferred hydrophilic chains
are hydrolyzed polyacrylonitrile chains and copolymers of
polyacrylamide and polysodium acrylate.
In addition to modified natural and regenerated polymers, the
hydrocolloid particle component may comprise wholly synthetic
hydrophilic particles. Examples of those now known in the art are
polyacrylonitrile fibers which may be modified by grafting moieties
thereon such as polyvinyl alcohol chains, polyvinyl alcohol itself,
hydrophilic polyurethane, poly(alkyl phosphonates), partially
hydrolyzed polyacrylamides (e.g., poly(N-N-dimethyl acrylamide),
sulfonated polystyrene, or a class of poly(alkylene oxide). These
highly hydrophilic synthetic polymers may be modified by other
chemical treatments such as cross-linking or hydrolysis. Further
examples known in the art are the non-ionic hydrophilic polymers
such as polyoxyethylene, polyoxypropylene and mixtures thereof
which have been suitably cross-linked, either chemically or by
irradiation. Still another more recent type is a derivative of
isobutylene-maleic anhydride copolymer.
Hydrophilic polymers formed from water-soluble acrylate monomers,
such as sodium, potassium, ammonium (or combinations of cations),
acrylate, may be placed on the absorbing layer by spraying or
otherwise placing a solution thereon followed by polymerization and
cross-linking, for example, by irradiation.
Other suitable superabsorbent includes naturally occurring
materials such as gums, and the like. Guar gum, acacia gum, and
locust bean gum are examples of suitable gums.
The absorbent article 20 of FIG. 2 has major surfaces 32 and 32b,
side edges 34, and end edges, not shown. The absorbent article may
have a partial outer wrap 30 of a fluid impervious material, which
covers at least one major surface 32 and the side edges 34 of the
absorbent article, and may also cover the end edges. This partial
outer wrap comprises a preferred construction of the absorbent
article, as the fluid impermeable layer retains the fluid in the
absorbent article, allowing time for the fluid to be absorbed by
the superabsorbent layers. In addition, in an absorbent article
utilizing this wrapped construction, the fluid impervious layer
hides of the off color appearance or texture of other absorbent
materials e.g., reground pulp, used in the absorbent article and
encapsulates and hides the gel-like nature of the superabsorbent
when wetted. This preferred absorbent article may also be provided
with a facing layer 36 on the other major surface 32b not covered
by the partial outer wrap.
FIG. 2A discloses another embodiment of the absorbent article of
the present invention shown schematically in FIG. 1. The absorbent
article shown generally at 20a comprises superabsorbent containing
layers 22a and internal wicking means 24a. The wicking means
comprises a wicking layer 26a and fluid transfer means 28a. As
shown in this embodiment, the fluid transfer means may comprise a
layer coextensive with the wicking layer. In this construction, the
wicking layer may be incorporated between two layers of fluid
transfer means, and this multilayer composite structure wound in an
S-shape about and around the superabsorbent containing layers. This
construction of the wicking means and of the absorbent article of
the present invention differs from that shown in FIG. 2 wherein the
fluid transfer means is disposed between the wicking layer and the
major surfaces of each superabsorbent layer. This embodiment may
also incorporate a fluid-impermeable layer 30 and a facing layer 36
comparable to those described at 30 and 36 of FIG. 2. When used as
a sanitary napkin the absorbent article may further comprise
adhesive strips 38 for attachment to an undergarment.
FIG. 3 shows another embodiment of the absorbent article of the
present invention, shown generally at 40. The absorbent article
shown here in cross-section comprises superabsorbent containing
layers 42 and an internal wicking means 44 which comprises a
wicking layer 46 wound about and between the superabsorbent
containing layers in an "e" shape. The wicking means comprises a
wicking layer 46 and a fluid transfer means 48. In the particular
embodiment shown, each of the superabsorbent containing layers has
been wrapped in a fluid transfer means such as tissue prior to the
winding of the wicking layer about and between the superabsorbent
containing layers. When the wrapping of the fluid transfer means
and the winding of the wick is completed, the wicking layer extends
across the major surfaces of the superabsorbent containing layers
and fluid transfer means are disposed between the wicking layer and
each major face of the superabsorbent containing layers. The
juxtapositioning of the wicking layer and fluid transfer means to
this superabsorbent containing layer provides an internal wicking
means for the superabsorbent containing layers. Optionally, this
embodiment of the absorbent article of the present invention may
also incorporate a facing layer 36 and a partial outer wrap 34 as
described in relation to FIGS. 2 and 2A.
The superabsorbent materials utilized in the present invention
comprise various hydrocolloid and hydrogel materials as
hereinbefore described which have the ability to absorb 10 to 30
times their own dry weight and preferably many hundreds of times
their own dry weight of fluids. Many superabsorbent materials are
known in the art and the present invention does not depend on the
chemical or physical structure of the superabsorbent, or the
structure of a composite wherein the superabsorbent is incorporated
with other materials, e.g., fibers in a fibrous layer. Because the
absorbent article of the present invention comprises discrete
superabsorbent layers, it avoids the "working" by folding and
bending of the fibrous layer or cellular foam layer which may cause
the superabsorbent to become disattached from the fibrous layer or
cellular foam, and agglomerate. In addition, the construction of
the absorbent article of the present invention provides an easier
method of manufacture than folding of the superabsorbent containing
layers and requires a lesser length of wicking material in the
wicking layer than would be utilized in a folded shape such as that
shown in U.S. Pat. No. 3,791,379.
FIG. 4 discloses a disposable diaper utilizing the absorbent
article of the present invention. The absorbent article of the
present invention may be utilized in many structures such as
sanitary napkins and dressings, as well as in various diaper
structures. FIG. 4 discloses a diaper structure shown generally at
50, said structure comprising an outer layer 52, an absorbent
article of the present invention 10, attached thereto, and tape
tabs 56. The diaper may further comprise a facing layer 58
comprising the inside surface of the diaper.
As shown in FIG. 5, when the absorbent article of the present
invention comprises a partial outer wrap 30 of fluid impermeable
material as shown with relation to absorbent articles 20 (or 40,
not shown) in FIGS. 2, 2A (or 3) above, it is not necessary that
the outer layer 62 of the diaper, shown generally at 60, be fluid
impermeable. In a preferred construction, both the outer layer 62
and the outer wrap 30 of the absorbent article comprise plastic
films. The securing of the absorbent article within the diaper
secures the two plastic films, reinforcing the outer layer of the
diaper. As the tape tabs 66 can be more easily peeled from the two
layer plastic laminate, the diaper may be opened without tearing
the plastic film outer layer which can render the adhesive tape tab
unusable as well as allowing the inner absorbent material of the
diaper to leak out. In addition, the cleanly peeled adhesive tape
tab is available to make a new diaper fastening. Also with this
absorbent article construction of the present invention having an
outer wrap 30, neither pulp nor superabsorbent gel may leak from
the diaper.
FIG. 6 shows the diaper of FIG. 5 view from the outer surface of
the diaper illustrating that the region wherein the outer layer 62
is juxtaposed to the partial outer wrap 30, reinforcing the outer
layer and enhancing the repositionability of the tape tabs, 66. In
the preferred embodiment shown, the diaper includes elastic
gathering means, in the leg regions. The facing 68 is a liquid
permeable nonwoven such as polyester and is laminated to the
backing or outer layer 62 around the edges of the product.
The foregoing description and drawings are illustrative but are not
to be taken as limiting. Other variations and modifications are
possible without departing from the spirit and scope of the present
invention.
* * * * *